Unveiling the mechanism of high-performance hydrogen evolution reaction on noble-metal-free (113)-faceted Ni3C: ab initio calculations

Abstract

To examine the reactivity of noble-metal-free Ni₃C towards hydrogen evolution reaction (HER), we report a comprehensive first-principles density functional theory (DFT) study on the stability, geometric structure, electronic characteristics, and catalytic activity for HER on the Ni₃C crystal (113) surfaces with different surface terminations, namely the C-rich and Ni-rich terminated surface of Ni₃C (113). The results indicate that C-rich and some stoichiometric surfaces are thermodynamically stable. The bridge-site of C-rich Ni₃C (113) is indispensable for HER because it not only displays improved electrocatalytic activity, but also possesses appropriate hydrogen adsorption energy, overpotential and robust stability. The ΔG_H (0.02 eV) and overpotential obtained by C-rich Ni₃C outperformed that obtained by Pt determined by computation (ΔG_H = −0.07 eV). Thus, the bridge-sites of C-rich Ni₃C (113) function as both excellent and stable active sites and adsorption/desorption sites. Increasing the density of active sites through doping or enlarging the surface area renders a prospective strategy to ameliorate the HER activity further. Overall, this study elucidates new insights into the surface properties of Ni₃C for HER from water splitting and opens up a fascinating avenue to optimize the performance of solar energy conversion devices by synthesizing preferentially exposed catalyst facets.